Brexit: Why can’t the EU and UK find a solution to the Irish backstop controversy?

Downing Street admitted the latest Brexit talks were “difficult” and “robust” – the acknowledged code for an almighty row – while an EU official branded the British stance “insane”.

After Geoffrey Cox, the attorney general, abandoned plans for a return trip to Brussels for another go, why exactly is a breakthrough to rescue Theresa May’s stalled deal proving so difficult?

The first point is that what the UK is now demanding is a million miles from what the Commons ordered in January, which was “replacing” the Irish backstop with “alternative arrangements”.

The prime minister gave up on that last month, and on trying to secure a “time limit” on, or a “unilateral exit clause” from, the backstop and, therefore, the EU customs union earlier this week.

This means Mr Cox is simply trying to hoover up a few crumbs from the table after Brussels swiped the cake – and, yet, failing to achieve even that.

All the UK is after now is for an already planned post-Brexit arbitration panel to be able to rule if the UK has found a solution to escape the backstop, hopefully quickly.

We would then enter what the EU has dubbed – prepare to scream in frustration – a “mini-backstop”, a stripped-down guarantee of no border infrastructure.

It didn’t take long for Brussels to say no, as it insists it must retain a veto over ending the backstop, not least because it decides the gateway to the precious single market.

Ms May believes Tory MPs, and even the Democratic Unionist Party, would swing behind her deal in next week’s repeat “meaningful vote” if Mr Cox can change his legal advice that the UK risks being trapped in the backstop indefinitely.

But, crucially, sources say Mr Cox believes the EU’s position would not allow him to change his advice – leaving the government with no card to play.

There are still a few days to go, and the prime minister may yet rush to Brussels on Sunday or Monday if there is any hope of breaking the impasse, but it doesn’t feel like it.

The government is braced for a defeat by 50 to 100 votes – but, given the 230-vote massacre last time, that might be optimistic.

Got an unanswered question about Brexit? Send it to editor@independent.co.uk and we’ll do our best to supply an answer in our Brexit Explained series